1. Field of the invention
The present invention relates to a gas-operated automatic firearm, particularly a shotgun.
2. Description of the Prior Art
Autoloading shotguns generally include a bolt mechanism linked to a piston and cylinder assembly which is operated by a portion of the gas generated on discharge of a round and bled from the gun barrel to the cylinder.
The gas port is generally arranged approximately in the median third of the bore, slightly more than halfway along the length of the barrel.
There are a few problems connected with auto-loading gas-operated shotguns.
A main problem of auto-loading shotguns is the necessity to fire shells of different power and to ensure a correct operation with the weakest shells, the gas port section is rather large to allow the passage of a sufficient portion of gas. Also the diameter of the piston has to be greater than that of the bore.
Another problem of conventional gas-operated shotguns is that the barrel must have a minimum length due to the forward position of the gas port. It is however desirable to provide auto-loading shotguns with a shorter barrel.
U.S. Pat. No. 4,102,242 discloses a gas-operated shotgun provided with a pair of gas cylinders mounted on opposite sides of the barrel at a somewhat forward position of the barrel. The cylinders have respective pistons engaging an inertial weight slidably mounted on the magazine. The inertial weight is connected to the bolt mechanism by a pair of action bars. The barrel of this shotgun must have a minimum length set by the forward position of gas cylinders and related gas ports.
The aim of the present invention is to provide a gas operated shotgun, wherein the length of the barrel can be selected as desired while always ensuring a perfect automatic operation.
Within the scope of this aim, an object of the invention is to provide a gas operated shotgun with an improved automatic operation with respect to conventional gas operated shotguns even, especially, for example, when firing low power ammunition.
A further object of the invention is to provide a gas-operated shotgun wherein the expansion chamber and the piston are less subject to clogging.